Terms

• Repo (repository): set of files
• Commit: snapshot of current version of files in a project/repo
• Diff: differences between one commit and another commit. Each Git version of a file is an accumulation of diffs
• SHA (Secure Hash Algorithm): a string of 40 letters and numbers assigned by Git to a commit to uniquely identify it
• Tag: a name you can assign to a version, e.g. “v.1.0.3” or “draft-01”

Advice

For each project:

• Assign it to one local directory
• Make it an RStudio project
• Make it a Git repository (see previous book section)

Workflow

• Work on your files locally
• Periodically make a commit
  • When a “significant” stage is reached
  • Include a short commit message motivating the change
• Periodically push commits to GitHub - makes current version of repo accessible to others
  • First pull so that you have the updated remote version

Workflow

Can you remember/guess what these commands do?

• git clone https://github.com/jennybc/happy-git-with-r.git
• git remote --verbose
• git add foo.txt : add foo.txt to the index (staging area)
• git commit --message "A commit message"
• git status

Can you remember/guess what these commands do?

• git log
• git log --oneline

Can you remember/guess what these commands do?

• git diff

• The rest of the list is covered in the next few chapters

Branching and merging

• For parallel work or experimenting with new features without interfering with the main project
• git branch issue-5
• git checkout issue-5
• git checkout -b issue-5
• Switching branch when you have incomplete work:
  • git commit --all -m "WIP"
  • git checkout main
  • git checkout issue-5
  • git reset HEAD^

Merging and handling conflicts

• git checkout main

• git merge issue-5

Merging and handling conflicts

• If something goes wrong: git merge --abort
• More info: https://git-scm.com/book/en/v2/Git-Branching-Basic-Branching-and-Merging

Fetching and pushing

• git fetch happygit: downloads the remote commits to your local repo without changing the local branch
• git fetch + git merge ≈ git pull
• Git pull vs git fetch: https://www.youtube.com/watch?v=T13gDBXarj0
• # push my local changes to the origin remote's main branch git push origin main

Upstream tracking branches

• git config --global push.default current

What are refs?

• References to specific commits (like pointers in programming). Examples:
  • a branch name
  • HEAD (a symbolic ref)
  • a tag (e.g., v1.4.2)

Relative refs

• HEAD~1 or HEAD^: the commit just before HEAD
• HEAD~3 or HEAD^^^: three commits before HEAD
• See more: https://git-scm.com/docs/gitrevisions